Wyniki wyszukiwania - Biblioteka Nauki

1

Determining the optimal solution treatment temperature of aluminum cast alloys by using quantitative analysis

100%

Kucharikova L. , Tillova E.

Archiwum Wiedzy Inżynierskiej

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2017

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tom T. 2, Nr 2

27--30

EN

Heat treatment of aluminum casts is necessary for achieving the desired properties of casts. Heat treatment caused changes in microstructure and substructure of materials and therefore it is necessary to control which changes are sufficient and which are insufficient. Morphology (shape, size and distribution) of microstructural features influence the properties of cast rapidly. Contribution describes influence of the heat treatment marking T4 - solution treatment in dependence on temperature (505, 515 a 525 °C) and holding time (2, 4, 8, 16 a 32 hour) on structure (α–phase, eutectic silicon, intermetallic phases) and mechanical properties (ultimate tensile strength - UTS and Brinell hardness - HBW) of A226 cast alloy. This cast alloy is made out of secondary aluminum. Secondary aluminum alloys are made of aluminum scrap. About 70 % of such material are used in the manufacture of casts. Therefore the strictly microstructure control of experimental material before and after heat treatment is necessary for declaration of cast properties. Nowadays manufacturers use the methods of quantitative analysis for quick control of microstructural features. This work present some of them.

2

Microstructural features evaluation of age-hardened A 226 cast alloy by image analysis

100%

Kucharikova L. , Tillova E.

Production Engineering Archives

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2017

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tom Vol. 17

3--8

EN

Age-hardening provides one of the most widely used mechanisms for the strengthening of aluminum alloys. The age-hardening involves three steps: solution treatment, quenching and aging. The temperature of solution treatment and aging is very important in order to reach desired properties of castings. The optimum temperature of solution treatment and aging led to formation microstructural features in form which does not lead to decreasing properties, but increasing ones. The major micro-structural features in A 226 cast alloys which are responsible for increasing properties are: eutectic Si particles, Cu-rich phases, Fe-rich phases and porosity. The increase of properties depends on morphology, size and volume of microstructural features. In order to assess age-hardening influence on microstructural features in A226 cast alloys were used as possibilities of evaluation by means of image analysis. Quantitative analysis decelerate changes in microstructure includes the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu) further increase in the hardness and tensile strength in the alloy. Changes of mechanical properties were measured in line with STN EN ISO.

3

Comparison of low and high frequency fatigue tests

80%

Vasko A. , Belan J. , Kucharikova L.

Production Engineering Archives

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2017

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tom Vol. 17

15--18

EN

The paper presents the results of low and high frequency fatigue tests carried out on nodular cast iron. The specimens of synthetic nodular cast irons from three different melts were studied in the high cycle fatigue region (from 105 to 108 cycles) using fatigue experimental equipments for low and high frequency cyclic loading. Low frequency fatigue tests were carried out at frequency f ≈ 120 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100; high frequency fatigue tests were carried out at frequency f ≈ 20 kHz using the ultrasonic fatigue testing device KAUP-ZU. Both fatigue tests were realised at sinusoidal cyclic push-pull loading (stress ratio R = –1) at ambient temperature (T = 20 ± 5 °C).

4

The assessment of castings quality using selected quantitative methods

80%

Kucharikova L. , Tillova E. , Zavodska D.

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tom Vol. 13, No. 4

7--10

EN

Aluminium alloys represent an important category of materials due to their high technological value and wide range of applications. The alloys of the Al-Si-Cu system have become increasingly important in recent years, mainly in automotive industry that uses secondary aluminium (recycled) in the form of various motor mounts, pistons, cylinder heads, heat exchangers, air conditioners due to their high strength at room and high temperature. This work deals with possibilities of quick and correct assessment of aluminium castings microstructure, especially focused on volume, size and shape of structural parameters – eutectic Si and intermetallic phases different chemical compositions. These structural parameters affect the properties of castings and it is important to study their features. The features were studied by using image analyser software NIS Elements.

5

A brief overview and metallography for commonly used materials in aero jet engine construction

80%

Belan J. , Vasko A. , Kucharikova L.

Production Engineering Archives

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2017

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tom Vol. 17

9--14

EN

Aluminium, titanium, and nickel base alloys are mostly and widely used for aircraft jet engine construction. A proper evaluation of its microstructure is important from working safety point of view. To receive a well prepared sample of microstructure, some important steps have to be undertaken. Except for proper grinding and polishing of a sample, structure developing is a significant step, too. In order to develop microstructure various chemical reagents were used to achieve the best results for microstructure evaluation. The chemical reagents were used according to the previous knowledge and some new ones were also tested. Aluminium AK4-1č, titanium VT – 8, and nickel VŽL – 14 and ŽS6 – U alloys were used as an experimental materials. Alloy AK4-1č is used for fan blade production with working temperatures up to 300°C. It is a forged piece of metal machined down into final shape by five-axe milling machine. Alloy VT – 8 is used for high pressure compressor rotor blade production with working temperatures up to 500°C. Blades are forged as well and finally grinded. Finally nickel base alloys VŽL – 14 and ŽS6 – U are used for turbine blade production with working temperatures up 950°C. Blades for turbine are casted into mould with reducible models.

6

Quality control of cylinder head casting

80%

Tillova E. , Chalupova M. , Kucharikova L.

Production Engineering Archives

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2017

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tom Vol. 14

3--6

EN

New challenges for the Aluminium alloys used for the production of castings for automotive engine components result from an evolutionary trend of internal combustion engines towards higher specific power output. Cylinder heads, in particular, have to withstand higher operating temperature and stress levels. Present work describes quality control of microstructure (Si-morphologhy and Si-size) and mechanical properties (UTS, elongation, Brinell hardness) of cylinder head casting as effect of different T6 heat treatment (solution heat treatment time - 2, 3, 4, 5, 6, 7 hours). The data obtained from this study will be used to improve process control, and to help the selection of heat treatment of the casting for future products.

7

Structural analysis of iron based intermetallic phases in secondary AlSi6Cu4 cast alloy

80%

Svecova I. , Tillova E. , Kucharikova L.

Production Engineering Archives

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2017

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tom Vol. 15

3--6

EN

The use of secondary aluminum alloys is increasing because it contributes to the decrease of production costs. However, these alloys contain bigger amount of iron. Iron has a negative effect and therefore its elimination is necessary in order to add some elements, which are also called correctors of iron. The most frequently used corrector is manganese. Another quite often used correctors are chromium, potassium, magnesium, vanadium. In the following work, vanadium is used as a corrector of iron phases. The application of vanadium in aluminum alloys has a positive impact on their mechanical properties, increases the tensile strength, ductility and hardness. As experimental material AlSi6Cu4 alloy was used. It was alloyed by master alloy AlFe10. After adding to the master alloy the iron content, the critical value in the alloy exceeded. Vanadium was added to AlSi6Cu4 alloy in different quantities. The image analysis (software NIS-Elements) was used for quantifying the amount of iron based intermetallic phases and determination of average values.

8

Employing various metallography methods at high temperature alloy fatigue tests evaluation

70%

Belan J. , Kucharikova L. , Vasko A. , Chalupova M. , Svecova I.

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tom Vol. 13, No. 4

11--15

EN

Microstructures of superalloys have dramatically changed throughout the years, as modern technology of its casting or forging has become more sophisticated. The first superalloys have polyedric microstructure consisting of gamma solid solution, some fraction of gamma prime and of course grain boundaries. As demands on higher performance of aero jet engine increases, the changes in superalloys micro-structure become more significant. A further step in microstructure evolution was directionally solidified alloys with columnar gamma prime particles. The latest microstructures are mostly monocrystalline, oriented in [001] direction of FCC gamma matrix. All microstructure changes bring necessity of proper preparation and evaluation of microstructure. Except for the already mentioned structures have gamma double prime and various carbides form can be seen. These structural parameters have mainly positive influence on important mechanical properties of superalloys. The paper deals with a microstructural evaluation of both groups of alloys – cast and as well as wrought. Micro-structure evaluation helps to describe mechanism at various loading and failure of progressive superalloys. Such an example where micro-structure evaluation is employed is fractography of failure surfaces after fatigue tests, which are examples of metallography evaluation de-scribed in this paper as a secondary objective.